Bone Resorption, Imaging and Bis-Phosphonates

The bis-phosphonates are a group of drugs which prevent the loss of calcium from bone and its transfer to the blood stream. Bis-phosphonates are ideally suited for the treatment of bone diseases because they readily bind to bones at active sites of bone metabolism. 

Ethane-l-hydroxy-1,1 diphosphonate (EHDP) (12.125a) and related bis-phosphonate compounds such as (12.125b-f) inhibit bone resorption and are used in the treatment of osteoporosis and other bone diseases [9,10]. 

Complexes of the diphosphonic acid (12.125b) with y-ray-emitting isotopes of technetium are useful for medical diagnostic work since they concentrate in the bone. The use of technetium diphosphonate complexes for bone imaging (MRl below) has revolutionised bone-scanning techniques. Technetium pyrophosphate complexes are less satisfactory since the P-O-P linkages are liable to hydrolysis by body enzymes [11,12]. 

Technetium ( Tc) radiopharmaceuticals such as (12.126) function as good myocardial imaging agents. Iron complexes of phosphorylated mono- and disaccharides will function as contrast agents in the MRI of the gastrointestinal tract [13]. 

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